Sheet material positioning method and apparatus

ABSTRACT

In order to minimize the amount by which a sheet material must be moved for positioning, using a small number of sensors, and to achieve improvement of the operation and stabilization of the positioning accuracy, the size of the sheet material is recognized in advance, a sensor, which requires the smallest amount of movement of the sheet material for positioning the sheet material at a predetermined position, is selected from a plurality of sensors based on the recognized size, and the sheet material is detected by the selected sensor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet material positioning method andapparatus, in which sheet materials having a plurality of sizes areconveyed in a predetermined conveying direction so as to be loaded ontoa surface plate, and the sheet materials are positioned at apredetermined position on the surface plate.

2. Description of the Related Art

A technique has been developed, in which a printing plate (hereinafter aphotopolymer plate) in which a photosensitive layer (e.g., aphotopolymer layer) is provided on a support is used, and in which animage is directly recorded on the photopolymer layer of the photopolymerplate by laser beams or the like. (This technique is used in anautomatic exposure apparatus for printing plates.)

In this technique, an image is rapidly recorded onto a photopolymerplate, and thus, photopolymer plates need to be sequentially sent.Accordingly, it is preferable that a plurality of photopolymer platesare stacked in advance at a predetermined position and ready to be used,and that the photopolymer plates are automatically taken out one by oneso as to be sent into an exposure section. After being sent into theexposure section, the photopolymer plates are preferably conveyed alonga predetermined proper conveying path.

The photopolymer plate needs to be wound onto a printing drum at thetime of printing, and in order to position the photopolymer plate on theprinting drum, an automatic exposure apparatus for printing platesincludes a process for forming a punch-hole in the photopolymer plate.The punching is carried out on a surface plate, which serves as a basefor the exposure of the photopolymer plate, and is also for thesub-scanning movement. And the punch-hole serves as reference at thetime of exposure.

Accordingly, the photopolymer plate delivered onto the surface platemust be positioned at a proper position.

In order to carry out the positioning, initially, an incline of thephotopolymer plate is corrected, parallelism of the punch-hole of thephotopolymer plate for a center line is corrected. Then, a direction ofthe photopolymer plate, in which the punch-hole is orthogonal to thecenter line, is determined based on inversion of output signals from aplurality of sensors (inversion from a photopolymer plate detected stateto a photopolymer plate undetected state, or inversion from theundetected state to the detected state), which sensors are provided atpositions, which are the corners of the photopolymer plate when thephotopolymer plate is at the proper position. Namely, the incline of thephotopolymer plate with respect to the center line of the surface plateon the surface plate is corrected, and the position of the photopolymerplate on the surface plate in a direction which is orthogonal to thecenter line is corrected by using the sensors.

However, the side of the photopolymer plate, which side is in thedirection orthogonal to the center line, may have various sizes whichare within a range from 400 mm to 745 mm in millimeter interval. Thus,if sensors are provided so as to be at the best position for the each ofrespective sizes of the photopolymer plates, an enormous number ofsensors are required. Therefore, a predetermined number of sensors aredisposed at predetermined positions within the above-described range(the predetermined number is a number which is fewer than the number ofsizes of the photopolymer plates). The positioning of the photopolymerplate is carried out on the basis of a calculation result from detectionresults by the sensor. If the sensors are disposed at random positionsin this way, the amount of movement for initially detecting a corner ofthe photopolymer plate by the sensor and the amount of movement obtainedby the computations for positioning the photopolymer plate at theappropriate position vary depending upon the size of the photopolymerplate. As a result, there are disadvantages that, for example, theoperation efficiency deteriorates, and the positioning accuracy variesdepending upon the size of the photopolymer plate.

SUMMARY OF THE INVENTION

In consideration of the above facts, it is an object of the presentinvention to obtain a sheet material positioning method and apparatus,in which, positioning is carried out by a small number of sensors and atthe time of positioning the sheet material, amount of movement forpositioning can be minimized, and in which, improvement of the operationand stabilization of the positioning accuracy can be archived.

A first aspect of the present invention is a sheet material positioningmethod, in which, sheet materials having a plurality of sizes areconveyed in a predetermined conveying direction so as to be loaded ontoa surface plate, and an incline and a position of the sheet material ina conveying direction of the sheet material with respect to a properposition are corrected, and the sheet material, whose incline andposition with respect to the proper position have been corrected, ispositioned at a predetermined position on the surface plate by beingmoved in a direction orthogonal to the conveying direction, by using aplurality of sensors for detecting at least one corner of the sheetmaterial; and wherein at least one dimension of the sheet material inthe direction orthogonal to the conveying direction has been recognizedin advance; and wherein a sensor, which requires the smallest amount ofmovement of the sheet material for positioning the sheet material at thepredetermined position, is selected from the plurality of sensors basedon the recognized dimension of the sheet material, and the corner of thesheet material is detected by the selected sensor.

According to the first aspect of the present invention, with respect tothe proper position, after the incline has been eliminated and thepositioning in the conveying direction of the sheet material has beencorrected, the sensor, which requires the smallest amount of movement ofthe sheet material for positioning, is selected based on the dimensionof the sheet material. As a result, the time for positioning the sheetmaterial can be shortened.

A second aspect of the present invention according to the first aspectis a sheet material positioning method, wherein, after the sheetmaterial has been loaded onto the surface plate, a pressing member,which has a portion that is parallel to a side of the sheet materialwhich side is orthogonal to the conveying direction, presses the sheetmaterial to the proper position, so that the incline and the position inthe conveying direction of the sheet material are correctedsimultaneously.

According to the second aspect of the present invention, with respect tothe proper position, the incline is eliminated and the positioning inthe conveying direction of the sheet material is corrected in thefollowing manner: After the sheet material has been loaded onto thesurface plate, a pressing member, which has a line connecting at leasttwo points, which line is parallel to a side of the sheet material whichside is orthogonal to the conveying direction, is moved to thepredetermined position, so that the incline and the positioning in theconveying direction of the sheet material are corrected simultaneously.In this way, the position of the side of the sheet material pressed bythe pressing member is fixed, and thus, the sheet material can be easilypositioned in the conveying direction thereof. However, sincepositioning of the sheet material in the direction which is orthogonalto the conveying direction on the basis of a center reference, if thesize of the sheet material varies, the position of the sheet material inthe direction which is orthogonal to the conveying directionrespectively varies. As a result, the positioning method described inthe first aspect is required, and the smaller the amount of movement ofthe sheet material for positioning, the shorter the time forpositioning.

A third aspect of the present invention according to the first or secondaspect is a sheet material positioning method, wherein the dimension ofthe sheet material in the direction orthogonal to the conveyingdirection has different values, the different values are on the basis ofa predetermined dimension of 10 mm or lower.

According to the third aspect of the present invention, the sheetmaterial has a number of different sizes, and thus, it is almostimpossible in a structural view to dispose sensors optimal for detectingthe respective corners of the sheet materials for each of the sizes.Therefore, for example, the smallest and the largest sheet materials areselected, and the sensors are disposed so as to be most suitable onlyfor the selected sheet materials. When the sheet material is of anothersize, after the corner thereof has been detected by one of the disposedsensors, the difference can be computed so that the sheet material isconveyed.

A fourth aspect of the present invention is a sheet material positioningapparatus, in which, sheet materials having a plurality of sizes areconveyed in a predetermined conveying direction so as to be loaded ontoa surface plate, and the sheet material is positioned at a predeterminedposition on the surface plate, the apparatus comprising: a correctingdevice, which corrects an incline and a position in the conveyingdirection of the sheet material with respect to a proper position; aplurality of sensors, which detect at least one corner of the sheetmaterial by movement of the sheet material in a direction orthogonal tothe conveying direction; a storing device, which stores at least onedimension of the sheet material in the direction orthogonal to theconveying direction in advance; a selecting device, which, based on thedimension stored in the storing device, selects a sensor from theplurality of sensors, that requires the smallest amount of movement ofthe sheet material for positioning the sheet material at thepredetermined position; and a movement controlling device, which movesthe sheet material in the direction orthogonal to the conveyingdirection based on the sensor selected by the selecting device, andwhich stops the movement of the sheet material in the directionorthogonal to the conveying direction when the sensor has detected thecorner of the sheet material.

According to the fourth aspect of the present invention, initially, theincline and the position in the conveying direction of the sheetmaterial with respect to the proper position are corrected by thecorrecting device. Next, the sensor, that requires the smallest amountof movement of the sheet material for positioning it at thepredetermined position, is selected from the plurality of sensors by theselecting device based on the dimension stored in the storing device.After that, by the movement controlling device, the sheet material ismoved in the direction orthogonal to the conveying direction using thesensor selected by the selecting device, and the movement of the sheetmaterial in the direction orthogonal to the conveying direction isstopped when the sensor has detected the corner of the sheet material.

In other words, since the size (dimension) of the conveyed sheetmaterial has been stored in the storing device in advance, which of theplurality of sensors is most suitable can be reliably determined. Whenthe sensor is selected based on the determination, the sensor, thatrequires the smallest amount of movement of the sheet material forpositioning, is reliably selected.

A fifth aspect of the present invention according to the fourth aspectis a sheet material positioning apparatus, wherein, the correctingdevice is formed of a pressing member, which has a portion that isparallel to a side of the sheet material which side is orthogonal to theconveying direction, and wherein, after the sheet material has beenloaded onto the surface plate, the pressing member presses the sheetmaterial to the proper position, so that the incline and the position inthe conveying direction of the sheet material are correctedsimultaneously.

According to the fifth aspect of the present invention, with respect tothe proper position, the incline has been eliminated and the position inthe conveying direction of the sheet material is corrected in thefollowing manner: After the sheet material has been loaded onto thesurface plate, a pressing member, which has a line connecting at leasttwo points, which line is parallel to a side of the sheet material whichside is orthogonal to the conveying direction, is moved to thepredetermined position, so that the incline and the position in theconveying direction of the sheet material are corrected simultaneously.In this way, the position of the side of the sheet material pressed bythe pressing member is fixed, and thus, the position in the conveyingdirection of the sheet material can be easily positioned.

A sixth aspect of the present invention according to the fourth or fifthaspect is a sheet material positioning apparatus, wherein the dimensionof the sheet material in the direction orthogonal to the conveyingdirection has different values, the different values are on the basis ofa predetermined dimension of 10 mm or lower.

According to the sixth aspect of the present invention, the sheetmaterial has a number of different sizes, and thus, it is almostimpossible in a structural view that the sensors are arranged so as tobe most suitable for detecting the respective corners of the sheetmaterials. Therefore, for example, the smallest and the largest sheetmaterials are selected, and the sensors are disposed so as to be mostsuitable only for the selected sheet materials. When the sheet materialis of another size, after the corner thereof has been detected by one ofthe disposed sensors, the difference can be computed so that the sheetmaterial is conveyed.

A seventh aspect of the present invention according to any one of thefourth to sixth aspects is a sheet material positioning apparatus,wherein the plurality of sensors include two sensors, which are disposedat positions corresponding to dimensions of smallest and largest sheetmaterials in the direction orthogonal to the conveying direction.

According to the seventh aspect of the present invention, when at leasttwo sensors, which correspond to the smallest and the largest sheetmaterials, are disposed, the sheet material can be positioned by beingmoved by an amount which is smaller than the difference between thesmallest and the largest sheet materials (smaller than a distance on thebasis of the difference between the smallest and the largest sheetmaterials).

An eighth aspect of the present invention according to any one of thefourth to sixth aspects is a sheet material positioning apparatus,wherein the plurality of sensors include three sensors, two sensors ofwhich are disposed at positions corresponding to dimensions of smallestand largest sheet materials in the direction orthogonal to the conveyingdirection, and one sensor other than the two sensors is disposed at aposition in substantially middle of the two sensors.

According to the eighth aspect of the present invention, in addition tothe seventh aspect, the sensor is added so as to correspond to amedium-sized sheet material whose size is between that of the smallestand the largest ones. As a result, the amount of movement forpositioning can be reduced, and further, for example, if the sensor atthe middle position is made movable, the sensor can be disposed inaccordance with the size of the sheet material which is frequently usedby the applied user.

A ninth aspect of the present invention according to any one of thefourth to sixth aspects is a sheet material positioning apparatus,wherein the plurality of sensors include CCD line sensors.

According to the ninth aspect of the present invention, when the CCDline sensors are disposed at predetermined positions, the position ofthe sheet material can be accurately recognized. Further, the pluralityof sensors may be closely arranged so as to form a group of sensors.

A tenth aspect of the present invention according to any one of thefourth to ninth aspects is a sheet material positioning apparatus,wherein the sheet material is a printing plate in which a photosensitivelayer is provided on a support.

According to the tenth aspect of the present invention, the printingplate in which the photosensitive layer is provided on the support isused as the sheet material. The printing plate is photosensitive, andthus, it needs to be positioned in a darkroom. Accordingly, automaticpositioning by the sensors is necessary. In this case, the positioningapparatus described in the fourth to ninth aspects is effective.

An eleventh aspect of the present invention according to the tenthaspect is a sheet material positioning apparatus, wherein, in a state inwhich the printing plate is positioned at the predetermined position, apunch-hole for positioning the printing plate at a mounting position ona printing drum is formed in the printing plate.

According to the eleventh aspect of the present invention, in order toform the punch-hole in the printing plate for positioning the printingplate at the mounting position on the printing drum, the positioningneeds to be accurately carried out. If the punch-hole is dislocated,color blurring or the like is caused, and as a result, the image qualityis deteriorates. Accordingly, the invention described in the tenthaspect, in which both positioning rapidity and positioning accuracy canbe archived, is effective.

A twelfth aspect of the present invention is a sheet materialpositioning method, in which, a sheet material is conveyed in apredetermined conveying direction so as to be loaded onto a surfaceplate, and the sheet material loaded onto the surface plate is moved ina direction orthogonal to the conveying direction, such that the sheetmaterial is positioned at a predetermined position on the surface plateby a plurality of sensors for detecting the sheet material; and whereinat least one dimension of the sheet material in the direction orthogonalto the conveying direction is recognized; and wherein a sensor, whichrequires the smallest amount of movement of the sheet material forpositioning the sheet material at the predetermined position, isselected from the plurality of sensors based on the recognized dimensionof the sheet material, and the sheet material is detected by theselected sensor.

A thirteenth aspect of the present invention according to the twelfthaspect is a sheet material positioning method, wherein, before the sheetmaterial loaded onto the surface plate is moved in the directionorthogonal to the conveying direction, the orientation and position ofthe sheet material are corrected so that the sheet material has apredetermined orientation with respect to the conveying direction andthe sheet material is positioned at a predetermined position in theconveying direction.

A fourteenth aspect of the present invention according to the twelfthaspect is a sheet material positioning method, wherein the corner of thesheet material is detected by the selected sensor.

A fifteenth aspect of the present invention is a sheet materialpositioning apparatus, in which, a sheet material is conveyed in apredetermined conveying direction so as to be loaded onto a surfaceplate, and the sheet material loaded onto the surface plate is moved ina direction orthogonal to the conveying direction, such that the sheetmaterial is positioned at a predetermined position on the surface plateby a plurality of sensors for detecting the sheet material, theapparatus comprising: a recognizing portion, which recognizes at leastone dimension of the sheet material in the direction orthogonal to theconveying direction; and a selecting portion, which, based on thedimension of the sheet material recognized by the recognizing portion,selects a sensor from the plurality of sensors, which requires thesmallest amount of movement of the sheet material for positioning thesheet material at the predetermined position; and wherein the sheetmaterial is detected by the selected sensor.

A sixteenth aspect of the present invention according to the fifteenthaspect is a sheet material positioning apparatus, wherein the corner ofthe sheet material is detected by the selected sensor.

A seventeenth aspect of the present invention according to the fifteenthaspect is a sheet material positioning apparatus further comprising astoring device, which stores the dimension of the sheet materialrecognized by the recognizing portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an overall structure of anautomatic exposure apparatus relating to the present embodiment.

FIG. 2 is a side view showing a state in which photopolymer plates andinterleaf sheets are loaded in a magazine.

FIG. 3 is a side view of a plate supplying section.

FIG. 4A is a plan view showing a portion of a conveying system of theplate supplying section.

FIG. 4B is a side view showing a portion of the conveying system of theplate supplying section.

FIG. 4C is a side view of an essential portion of an interleaf sheetconveying portion.

FIG. 5 is a perspective view showing a delivery portion for passing theprinting plates between different conveying systems of the platesupplying section.

FIG. 6A is a plan view of a surface plate.

FIG. 6B is a side view of the surface plate.

FIG. 7A is a side view showing an operation of a discharging mechanismportion at the beginning thereof.

FIG. 7B is a side view showing an operation of the discharging mechanismportion in a state in which the photopolymer plate is lifted up.

FIG. 7C is a side view showing an operation of the discharging mechanismportion at the time of discharging the photopolymer plate.

FIG. 8 is a plan view showing an arrangement structure of sensors forcentering.

FIG. 9 is a characteristic chart showing relationships between sizes ofthe photopolymer plates and distances from each of the sensors torespective detected corners of each of the photopolymer plates.

FIG. 10 is a control block diagram for centering the photopolymer plate.

FIG. 11 is a plan view showing a positional relationship between thephotopolymer plates and the sensors.

FIG. 12 is a plan view showing another arrangement structure of sensorsfor centering.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(Overall Structure)

An automatic exposure apparatus 100 for photopolymer plates, whichapparatus relates to this embodiment, is shown in FIG. 1.

The automatic exposure apparatus 100 consists of a plate supplyingsection 108, which includes a plate accommodating portion 104 thataccommodates photopolymer plates 102 (see FIG. 2) loaded on a trolley200, and includes a sheet feeding portion 106 that carries out thephotopolymer plate 102 accommodated in the plate accommodating portion104; a surface plate 110 on which the photopolymer plate 102 ispositioned and held; and an exposure section 112 which records an imageon the photopolymer plate 102 positioned on the surface plate 110.

An automatic developing apparatus 116 can be provided at a downstreamside of the automatic exposure apparatus 100 via a buffer portion 114.Thus, all of the plate-supplying, exposing and developing processes canbe automatically carried out.

As shown in FIG. 3, the plate accommodating portion 104 can accommodatethe trolley 200 against which a plurality of photopolymer plates 102 arepropped. As shown in FIG. 2, a protective interleaf sheet 118 isprovided on a surface of each photopolymer plate 102, and as a result,the photopolymer plates 102 and the interleaf sheets 118 are alternatelysuperimposed.

The plate accommodating portion 104 forms a floor portion 104A at ahigher position than a ground surface, and the trolley 200 is structuredso that it can be mounted onto the floor portion 104A from the groundsurface. Specifically, the trolley 200 is supported to the groundsurface via casters 120, and each of the casters 120 can move toprotruding positions (i.e., the positions shown with notched lines inFIG. 3) or to storing positions (i.e., the positions shown with solidlines in FIG. 3) with respect to the trolley 200.

At the same time when the casters 120 move to the storing positions soas to be upwardly collapsed toward the plate accommodating portion 104due to a storing operation, auxiliary rollers 212 correspond to thefloor portion 104A. Thereafter, the trolley 200 is supported to thefloor portion 104A via the auxiliary rollers 212.

The sheet feeding portion 106 is provided above the plate accommodatingportion 104. The sheet feeding portion 106 is structured so as toalternately take up the photopolymer plate 102 and the interleaf sheet118 from a state in which they are stacked, and send them to a commonconveying portion 128. The sheet feeding portion 106 includes a sucker124, which sucks the photopolymer plate 102 and the interleaf sheet 118.Further, a suction fan 126 is separately provided near the sucker 124,as an auxiliary means for sucking the interleaf sheet 118. The sucker124 and the suction fan 126 can move integrally toward and away from asurface of an interleaf sheet 118 or of a photopolymer plate 102, whichare stacked together.

When the photopolymer plate 102 is sucked and held, the sucker 124 isdisposed so as to be in contact with the photopolymer plate 102. On theother hand, when the interleaf sheet 118 is sucked and held, the suctionfan 126 is disposed so as to be slightly away from (or may be disposedso as to be in contact with) the interleaf sheet 118, and only thesuction fan 126 is operated. The suction fan 126 sucks up only theinterleaf sheet 118 which is lighter and thinner than the photopolymerplate 102, and thereafter, the sucker 124 sucks the interleaf sheet 118.As a result, when the interleaf sheet 118 is sucked, double suction(i.e., suction of the interleaf sheet 118 together with the underlyingphotopolymer plate 102) is prevented.

The plate supplying section 108 largely consists of the common conveyingportion 128, which receives the photopolymer plate 102 or the interleafsheet 118 from the sheet feeding portion 106 and conveys it; aphotopolymer plate conveying portion 130, which receives thephotopolymer plate 102 and sends it to the surface plate 110; aninterleaf sheet conveying portion 134, which receives the interleafsheet 118 and sends it to an interleaf sheet accommodating portion 132(loaded on the trolley 200); and a conveyance switch portion 136, whichguides the photopolymer plate 102 or the interleaf sheet 118 from thecommon conveying portion 128 to either the photopolymer plate conveyingportion 130 or the interleaf sheet conveying portion 134 by a switchingoperation.

Specifically, as the photopolymer plates 102 and the interleaf sheets118 are alternately stacked, each time the photopolymer plate 102 or theinterleaf sheet 118 is sucked at the sheet feeding portion 106, theconveyance switch portion 136 switches and conveys the photopolymerplate 102 or the interleaf sheet 118 to the respective predetermineddirection.

As shown in FIG. 4A, the common conveying portion 128, the photopolymerplate conveying portion 130 and the conveyance switch portion 136 are aconveying system in which skewered rollers 138 and narrow belts 140 arecombined, and this conveying system is formed so as to mainly convey thephotopolymer plate 102 (see FIG. 4B). Specifically, the photopolymerplate 102 is conveyed with a strong nipping force of the skeweredrollers 138, and the narrow belts 140 serve as guide panels which movesynchronously with the conveyance.

On the other hand, as shown in FIG. 4C, the interleaf sheet conveyingportion 134 is a conveying system including only the narrow belts 140.This conveying system is structured so as to convey the interleaf sheet118 with a weak nipping force of the narrow belts 140.

As shown in FIG. 5, at a portion for delivery from one conveying portionto another, end portions thereof alternately protrude in a skeweredconfiguration, such that a recessed end portion of one corresponds to aprotruded end portion of the other (i.e., both end portions have acoaxial common conveying path). As a result, when the photopolymer plate102 and the interleaf sheet 118 are delivered, they are prevented frombeing caught in the skewered rollers 138 and the narrow belts 140.

As shown in FIG. 3, the interleaf sheet 118 conveyed by the interleafsheet conveying portion 134 is guided to the interleaf sheetaccommodating portion 132 provided on the trolley 200. An insertionopening 142 for the interleaf sheets 118, which is provided at an upperportion of the interleaf sheet accommodating portion 132, is providedwith a pair of rollers 144. The rollers 144 drive rotatively at a linearvelocity, which is slightly higher (about 1.1 times) than the conveyancevelocity of the interleaf sheet conveying portion 134. Accordingly, whenthe interleaf sheet 118 is between the interleaf sheet conveying portion134 and the rollers 144, the interleaf sheet 118 is conveyed whilemaintaining a predetermined tense state. As a result, jamming resultingfrom slackness and the like is prevented.

Tapered guide panels 146, by which the width (in the thickness directionof the interleaf sheet 118) is gradually narrowed, are provided at anupstream side of the insertion opening 142. A charge removing brush 148is attached to each of the tapered guide panels 146 which oppose eachother, and the charge removing brushes 148 remove charge from theinterleaf sheet 118 inserted into the insertion opening 142.

The pair of rollers 144 are arranged in a skewered configuration, andpartition panels 150 are provided along the protruding portions whichresult from the skewered configuration. As a result, even if a part ofthe interleaf sheet 118, which has been accommodated in the interleafsheet accommodating portion 132, touches the rollers 144, the partitionpanels 150 prevent the interleaf sheet 118 from being caught in therollers 144.

As shown in FIG. 1, the photopolymer plate 102 conveyed by thephotopolymer plate conveying portion 130 leaves the photopolymer plateconveying portion 130 in a horizontal conveyance state, and is deliveredto the surface plate 110.

A height of a top surface of the surface plate 110 is lower than ahorizontal conveyance height of the photopolymer plate conveying portion130, and there is a slight gap therebetween in the conveying direction.Accordingly, when the photopolymer plate 102 is discharged from thephotopolymer plate conveying portion 130, the photopolymer plate 102lands on the surface plate 110 in a state in which it hangs slightly,and a rear end portion of the photopolymer plate 102 in the conveyingdirection is positioned at a more upstream position than the surfaceplate 110. As shown in FIG. 6B, a temporary support plate 154, which isprovided on a moving body 152 that can move toward and away from thesurface plate 110, is disposed at this upstream position, and thetemporary support plate 154 prevents the photopolymer plate 102 fromhanging.

A pressing plate 156 for pressing the rear end portion of thephotopolymer plate 102 in the conveying direction is provided at a partof the temporary support plate 154. When the rear end portion of thephotopolymer plate 102 is pressed by the pressing plate 156, the inclineof the photopolymer plate 102 is eliminated, and the photopolymer plate102 can be sent to a predetermined reference position in the conveyingdirection. When the photopolymer plate 102 is at the reference position,the rear end portion thereof in the conveying direction slightly jutsout from the surface plate 110.

In the reference position, sensors 158 are provided at a plurality ofpositions including both corners of the rear end portion of thephotopolymer plate 102 in the conveying direction. When the rear endportion of the photopolymer plate 102 in the conveying direction isdetected by the sensors 158, the pressing of the pressing plate 156 isdiscontinued. Further, the sensors 158 are also applied for detectingthe position of the photopolymer plate 102 in the transverse directionof conveyance. Specifically, the corners of the photopolymer plate 102are adjusted so as to be in line with the sensors 158 by movement of thesurface plate 110 in the transverse direction of conveyance, and thedetected position is registered as a start position of the photopolymerplate 102.

The position of the photopolymer plate 102 moved to the start positionis determined relative to a starting position of scanning exposure atthe exposure section 112. The photopolymer plate 102 is sucked and heldin this state by suction grooves 110A (see FIG. 6A) provided at thesurface plate 110.

A punch-hole is formed in the photopolymer plate 102 which is sucked andheld, by a puncher 160 (see FIG. 6B) provided on the moving body 152.

The surface plate 110 can move back and forth at a uniform velocitybetween a first position (see the position shown with solid lines inFIG. 1), at which the photopolymer plate 102 is received from thephotopolymer plate conveying portion 130, and a second position (see theposition shown with notched lines in FIG. 1), at which the photopolymerplate 102 is accommodated in the exposure section 112. (Movement in thetransverse direction of the conveyance for positioning also takes placein this back and forth manner.) At the exposure section 112, a scanningunit 164 is provided above the conveying path of the surface plate 110.In the scanning unit 164, laser beams which are light-controlled inaccordance with image signals are primarily scanned (in the directionorthogonal to the conveying direction of the surface plate 110). On theother hand, forward conveyance of the surface plate 110 is a movementfor secondary scanning. As a result, an image is recorded onto thephotopolymer plate 102 on the surface plate 110 during the forwardconveyance to the exposure section 112, and then, the photopolymer plate102 is returned to the original position by return conveyance. Thephotopolymer plate 102 on the surface plate 110, which has been returnedto the original position, is released from the state of being sucked andheld.

When the image has been recorded on the photopolymer plate 102 and thesurface plate 110 has been returned to the original position, adischarging mechanism portion 166, which has been on standby at the rearend portion side of the photopolymer plate 102 in the direction that theplate is conveyed by the photopolymer plate conveying portion 130,passes over the surface plate 110 so as to move to a front end portionside of the photopolymer plate 102 in the conveying direction (see FIG.7A).

Hook portions 166A for loading the rear end portion of the photopolymerplate 102 in the conveying direction are formed at the dischargingmechanism portion 166. The rear end portion of the photopolymer plate102 which juts out from the surface plate 110 is lifted up by thetemporary support plate 154 provided on the moving body 152 (see FIG.7B), and the discharging mechanism portion 166 is moved in the directionthat the photopolymer plate 102 is conveyed. As a result, thephotopolymer plate 102 is engaged with the hook portions 166A, and whilethe discharging mechanism portion 166 is moved, the photopolymer plate102 is conveyed to a downstream side of the surface plate 110 (see FIG.7C). The buffer portion 114 and further the automatic developingapparatus 116 are provided at this downstream side. While the differencebetween a discharging speed at the discharging mechanism portion 166 anda conveying speed at the automatic developing apparatus 116 is absorbedby the buffer portion 114, the photopolymer plate 102 is smoothly sentout.

(Arrangement Structure of Sensors)

Arrangement structure of sensors 158 which are disposed in the vicinityof the surface plate 110 is shown in FIG. 8. If the direction in whichthe photopolymer plate 102 is conveyed from the photopolymer plateconveying portion 130 is direction A, the four sensors 158 (hereinafter,158A, 158B, 158C and 158D respectively when referred to individually)are disposed along the direction which is orthogonal to the direction A.

These sensors are disposed so that the two inside sensors 158B and 158Chave a pitch-size of 380 mm, and the two outside sensors 158A and 158Dhave a pitch-size of 670 mm. A central position between the sensors 158Band 158C coincides with a central position between the sensors 158A and158D.

The sensors 158B and 158C serve as sensors for detecting an incline ofthe photopolymer plate 102 (with respect to the direction A). The sensor158B is also used for detecting the position of the photopolymer plate102 in the transverse direction of conveyance (in a direction which isorthogonal to the direction A), and the sensor 158C is only used fordetecting the incline of the photopolymer plate 102.

Therefore, in practice, the three sensors 158A, 158B and 158D areapplied for detecting the position of the photopolymer plate 102 in thetransverse direction of conveyance.

(Positioning Control System Using Sensors)

FIG. 9 shows relationships between sizes of the photopolymer plates 102having various sizes, and distances from respective detected corners ofeach of the photopolymer plates 102 to each of the sensors 158, when thephotopolymer plates 102 are sent from the photopolymer plate conveyingportion 130.

When the photopolymer plate 102 is moved in the transverse direction ofconveyance, each of the sensors 158 switches from a photopolymer plate102 detected state (On) to a photopolymer plate 102 undetected state(Off), or may switch from the undetected state (Off) to the detectedstate (On). In this embodiment, the corner of the photopolymer plate 102is detected in the following situations:

1. for detection by the sensor 158A: when it is switched from On to Off;

2. for detection by the sensor 158B: when it is switched from On to Off;and

3. for detection by the sensor 158D: when it is switched from Off to On.

The above definitions are predetermined, and thereby, for example, evenif the switching characteristics of the sensors include hysteresis orthe like, corners of the photopolymer plates 102 can be accuratelydetected.

When the characteristics of each of the sensors 158 shown in FIG. 9 arelooked at with the above definitions 1-3 in consideration, it can beseen that, in a case of the photopolymer plate 102 having a size rangingfrom 400 mm to 525 mm, the sensor 158B is closest to the detected cornerof the photopolymer plate 102; in a case of a size ranging from 525 mmto 670 mm, the sensor 158D is closest thereto; and in a case of a sizeranging from 670 mm to 740 mm, the sensor 158A is closest thereto. InFIG. 11, for example, in the case of the photopolymer plate L having a670 mm size in the transverse direction of the conveyance, the distancebetween the corner C1 of the photopolymer plate L and the sensor 158A iszero, the distance between the corner C2 of the photopolymer plate L andthe sensor 158D is zero, the distance between the corner C1 of thephotopolymer plate L and the sensor 158B is +145 mm.

In this embodiment, a controlling portion 250 for positioning, which isshown in FIG. 10, is provided with a memory 252, which stores in advancethe size of the photopolymer plate 102 sent from the photopolymer plateconveying portion 130. In accordance with the size of the photopolymerplate 102 stored in the memory 252, the most suitable one of the sensors158 (i.e., the sensor which is closest to the detected corner of thephotopolymer plate 102) is selected in advance and applied. A driver 254for moving the surface plate 110 and a driver 256 for moving thepressing plate 156 are connected to the controlling portion 250.

Hereinafter, operation of this embodiment will be described.

When the photopolymer plate 102 is sent from the photopolymer plateconveying portion 130 onto the surface plate 110, the photopolymer plate102 is separated from the final conveying roller of the photopolymerplate conveying portion 130, and is loaded on the surface plate 110 suchthat it is slid down. Therefore, the position of the photopolymer plate102, which has been slid down on the surface plate 110, relative to thesurface plate 110 is irregular (different each time), and thus, anincline of the photopolymer plate 102 and the position of thephotopolymer plate 102 in a direction which is along the conveyingdirection from the photopolymer plate conveying portion 130 arecorrected first.

When the photopolymer plate 102 is discharged from the photopolymerplate conveying portion 130, the photopolymer plate 102 lands on thesurface plate 110 in the state in which it hangs slightly, and thehanging portion of the photopolymer plate 102 is supported by thetemporary support plate 154. In this state, the rear end portion of thephotopolymer plate 102 is pressed by the pressing plate 156, and as aresult, the incline of the photopolymer plate 102 with respect to theconveying direction of the photopolymer plate 102 is eliminated.Further, when the photopolymer plate 102 is pressed by a predetermineddegree by the pressing plate 156, the photopolymer plate 102 can be sentto the predetermined reference position in the conveying direction. Ifthe edge of the rear end portion of the photopolymer plate 102 in theconveying direction is detected by the sensors 158B and 158C, it can berecognized that the photopolymer plate 102 has been positioned at thesuitable position. (When the sensors 158B and 158C detect thephotopolymer plate 102 at the same time, it is judged that thephotopolymer plate 102 is positioned at the predetermined referenceposition without incline.)

After the photopolymer plate 102 has been positioned at the referenceposition, the position of the photopolymer plate 102 in the transversedirection of conveyance is detected by using one of the sensors 158A,158B and 158D.

In this case, in this embodiment, the size of the photopolymer plate 102loaded on the surface plate 110, which size is stored in the memory 252of the controlling portion 250 for positioning, is read out, and basedon this size, the most suitable sensor is selected using acharacteristic chart in FIG. 9. The most suitable sensor is a sensor,which clears the above-mentioned conditions 1-3 and which is closest tothe detected corner of the photopolymer plate 102.

When the selected sensor (sensor 158A, 158B or 158D) detects the cornerof the photopolymer plate 102 by movement of the surface plate 110 (byrelative movement of the surface plate 110 and the photopolymer plate102) in the transverse direction of conveyance, a punch-hole is formedin the photopolymer plate 102, and this position is registered as astart position at the time of exposing the photopolymer plate 102.

After that, exposure is started at the time when the surface plate 110has moved by a predetermined amount from the start position to theexposure section 112.

As described above, in this embodiment, the sensor, which requires thesmallest amount of movement for detecting the corner of the photopolymerplate 102, is selected from the three sensors 158A, 158B and 158D forcentering the photopolymer plate 102 (for positioning the photopolymerplate 102 in the transverse direction of conveyance). As a result,positioning operation can be rapidly carried out, and the operationefficiency can be improved.

In this embodiment, the three sensors 158A, 158B and 158D are used forcentering. However, if at least two sensors are disposed so that one ofthe sensors, which requires smaller amount of movement, is selected, theeffect of the present invention can be obtained. Further, if four ormore sensors are disposed, the amount of movement for positioning can bereduced even more.

Furthermore, in this embodiment, the sensors 158A, 158B and 158D arefixed. However, at least one of the sensors (preferably, the sensor 158Clocating in the middle) may be structured so as to move in the directionof movement for positioning (in the transverse direction of conveyance),so that the sensor can move to the most suitable position based on thesize of the photopolymer plate 102, which size is stored in the memory252. (In FIG. 12, the sensor 158C can move along a directions indicatedby an arrow T.) Moreover, a large number of sensors may be closelyarranged.

Each of the sensors 158A, 158B and 158D may be a linear CCD sensor,respectively.

As described above, the sheet material positioning method and apparatusrelating to the present invention has superior effects that, at the timeof positioning the sheet material, a small number of sensors can be usedfor positioning and the amount of movement for positioning can beminimized, and that, improvement of the operation and stabilization ofthe positioning accuracy can be achieved.

What is claimed is:
 1. A sheet material positioning method, in which,sheet materials having a plurality of sizes are conveyed in a conveyingdirection so as to be loaded onto a surface plate, the methodcomprising: (a) loading a sheet material onto the surface plate; (b)removing an incline of the sheet material on the surface plate relativeto the conveying direction; (c) moving the sheet material relative tothe surface plate to a first predetermined position in the conveyingdirection; (d) moving the sheet material together with the surface platein a direction orthogonal to the conveying direction, such that thesheet material is positioned at a second predetermined position; (e)recognizing at least one dimension of the sheet material in thedirection orthogonal to the conveying direction before step (d); (f)selecting a sensor from a plurality of sensors, the selected sensorbeing closest to at least one corner of the sheet material based on therecognized dimension of the sheet material; and (g) detecting the cornerof the sheet material by the selected sensor.
 2. A sheet materialpositioning method according to claim 1, wherein steps (b) and (c) areperformed simultaneously by a pressing member, which has a portion thatis orthogonal to the conveying direction, pressing the sheet material tothe first predetermined position.
 3. A sheet material positioning methodaccording to claim 1, wherein the dimension of the sheet material in thedirection orthogonal to the conveying direction has different values,the different values are on the basis of a predetermined dimension of 10mm or lower.
 4. A sheet material positioning apparatus, in which, sheetmaterials having a plurality of sizes are conveyed in a predeterminedconveying direction so as to be loaded onto a surface plate, saidapparatus comprising: a correcting device, which (1) removes an inclineof the sheet material on the surface plate relative to the conveyingdirection, and (2) moves the sheet material relative to the surfaceplate to a first predetermined position in the conveying direction; aplurality of sensors, which detect at least one corner of the sheetmaterial by movement of the sheet material in a direction orthogonal tothe conveying direction; a storing device, which stores at least onedimension of the sheet material in the direction orthogonal to theconveying direction; a selecting device, which, based on the dimensionstored in said storing device, selects a sensor from said plurality ofsensors, the selected sensor being closest to the at least one corner ofthe sheet material for positioning the sheet material at a secondpredetermined position; and a movement controlling device, which movesthe sheet material in the direction orthogonal to the conveyingdirection based on the sensor selected by said selecting device, andwhich stops the movement of the sheet material at the secondpredetermined position when the selected sensor has detected the atleast one corner of the sheet material.
 5. A sheet material positioningapparatus according to claim 4, wherein, said correcting device is apressing member, which has a portion that is orthogonal to the conveyingdirection, and wherein, after the sheet material has been loaded ontothe surface plate, the pressing member presses the sheet material to thefirst predetermined position.
 6. A sheet material positioning apparatusaccording to claim 4, wherein the dimension of the sheet material in thedirection orthogonal to the conveying direction has different values,the different values are on the basis of a predetermined dimension of 10mm or lower.
 7. A sheet material positioning apparatus according toclaim 4, wherein said plurality of sensors include two sensors, whichare disposed at positions corresponding to dimensions of smallest andlargest sheet materials in the direction orthogonal to the conveyingdirection.
 8. A sheet material positioning apparatus according to claim4, wherein said plurality of sensors include three sensors, two sensorsof which are disposed at positions corresponding to dimensions ofsmallest and largest sheet materials in the direction orthogonal to theconveying direction, and one sensor other than said two sensors isdisposed at a position in substantially a middle of said two sensors. 9.A sheet material positioning apparatus according to claim 4, whereinsaid plurality of sensors include CCD line sensors.
 10. A sheet materialpositioning apparatus according to claim 4, wherein the sheet materialis a printing plate in which a photosensitive layer is provided on asupport.
 11. A sheet material positioning apparatus according to claim10, further comprising a puncher for forming a punch-hole, forpositioning the printing plate at a mounting position on a printingdrum, in the printing plate.
 12. A sheet material positioning method, inwhich, a sheet material is conveyed in a predetermined conveyingdirection so as to be loaded onto a surface plate, and the sheetmaterial loaded onto the surface plate is moved in a directionorthogonal to the conveying direction, such that the sheet material ispositioned at a predetermined position on the surface plate by aplurality of sensors for detecting the sheet material, the methodcomprising: recognizing at least one dimension of the sheet material inthe direction orthogonal to the conveying direction; selecting a sensor,from the plurality of sensors, which is closest to at least one cornerof the sheet material for positioning the sheet material at thepredetermined position, wherein the selection is based on the recognizeddimension of the sheet material; and detecting the sheet material by theselected sensor.
 13. A sheet material positioning method according toclaim 12, further comprising: correcting the orientation and position ofthe sheet material so that the sheet material has a predeterminedorientation with respect to the conveying direction and the sheetmaterial is positioned at a predetermined position in the conveyingdirection.
 14. A sheet material positioning method according to claim12, wherein the corner of the sheet material is detected by the selectedsensor.
 15. A sheet material positioning apparatus, in which, a sheetmaterial is conveyed in a predetermined conveying direction so as to beloaded onto a surface plate, and the sheet material loaded onto thesurface plate is moved in a direction orthogonal to the conveyingdirection, such that the sheet material is positioned at a predeterminedposition on the surface plate by a plurality of sensors for detectingthe sheet material, said apparatus comprising: a recognizing portion,which recognizes at least one dimension of the sheet material in thedirection orthogonal to the conveying direction; and a selectingportion, which, based on the dimension of the sheet material recognizedby said recognizing portion, selects a sensor from the plurality ofsensors, the selected sensor being closest to at least one corner of thesheet material for positioning the sheet material at the predeterminedposition; wherein the sheet material is detected by the selected sensor.16. A sheet material positioning apparatus according to claim 15,wherein the corner of the sheet material is detected by the selectedsensor.
 17. A sheet material positioning apparatus according to claim 15further comprising a storing device, which stores the dimension of thesheet material recognized by said recognizing portion.